CANBERRA -- Rising temperatures will leave millions more people hungry by 2080 and cause critical water shortages in China and Australia, as well as parts of Europe and the United States, according to a new global climate report.

By the end of the century, climate change will bring water scarcity to between 1.1 and 3.2 billion people as temperatures rise by 2 to 3 Celsius (3.6 to 4.8 Fahrenheit), a leaked draft of an Intergovernmental Panel on Climate Change (IPCC) report said.

The report, due for release in April but detailed in The Age newspaper, said an additional 200 million to 600 million people across the world would face food shortages in another 70 years, while coastal flooding would hit another 7 million homes.

"The message is that every region of the earth will have exposure," Dr Graeme Pearman, who helped draft the report, told Reuters on Tuesday.

"If you look at China, like Australia they will lose significant rainfall in their agricultural areas," said Pearman, the former climate director of Australia's top science body, the Commonwealth Scientific and Industrial Research Organisation.

Africa and poor countries such as Bangladesh would be most affected because they were least able to cope with greater coastal damage and drought, said Pearman.

The IPCC was set up in 1988 by the World Meteorological Organisation and the U.N. Environment Programme to guide policy makers globally on the impact of climate change.

The panel is to release a report on Friday in Paris forecasting global temperatures rising by 2 to 4.5 Celsius (3.6 to 8.1 Fahrenheit) above pre-industrial levels by 2100, with a "best estimate" of a 3C (5.4 F) rise.

That report will summarise the scientific basis of climate change, while the April draft details the consequences of global warming and options for adapting to them.

The draft contains an entire chapter on Australia -- which is in the grip of its worst recorded drought -- warning the country's Great Barrier Reef would become "functionally extinct" because of coral bleaching.

As well, snow would disappear from Australia's southeast alps, while water inflows to the Murray-Darling river basin, the country's main agricultural region, would fall by 10 and 25 percent by 2050.

In Europe, glaciers would disappear from the central Alps, while some Pacific island nations would be hit hard by rising sea levels and more frequent tropical storms.

"It's really a story of trying to assess in your own region what your exposure will be, and making sure you have ways to deal with it," said Pearman.

On the positive side, Pearman said there was an enormous amount the international community could do to avert climate change if swift action was taken.

"The projections in the report that comes out this week are based on the assumption that we are slow to respond and that things continue more-or-less as they have in the past."